Boiler temperature sensor

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Old 12-26-13, 01:50 PM
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Boiler temperature sensor

I'm having an issue with my Logamatic R 2107 boiler temperature sensor. The temperature inside the boiler will sometimes rise 30-50F degrees after the boiler heating cycle ends. This will typically occur when all zone valves are closed and the outside air temperature is sufficiently cold (shutting down near BLR TEMP - MAX TEMP setting, currently set to 172F).

When zone valves are open, the temp/psi gauge on the supply line seems to respond more quickly than the internal probe and be perhaps 20 degrees warmer than the boiler temperature initially. The Logamatic sensor does obey the correct shut off temp, whether it be on the "curve" when below 14F outside or near the MAX TEMP setting below 14F. However, it seems as though the boiler temperature sensor is not accurately reading the current temp, causing the boiler to overheat the water.

The PSI of the system has also been high - the pressure relief valve has tripped 4 times in the last couple of weeks. Generally it has been 25-32PSI when in space heating mode and drops back to 12PSI when DHW has priority. I suspect the two issues could be related.

system:
Buderus GA124
Logamatic R 2107
LT 160 WH

single circuit with 4 honeywell zone valves controlled through Taco relay panel - 4 honeywell thermostats - no buderus room sensors. The circulator pump only runs when at least one of the zones calls for heat.

This is my first winter in the home so I have no idea whether the temperature response is normal, but occasionally seeing 210F on the logamatic boiler temperature reading concerns me, as does the water coming from the PRV.
 
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Old 12-26-13, 03:25 PM
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The temperature inside the boiler will sometimes rise 30-50F degrees after the boiler heating cycle ends. This will typically occur when all zone valves are closed and the outside air temperature is sufficiently cold (shutting down near BLR TEMP - MAX TEMP setting, currently set to 172F).
This MAY BE 'normal'. Not saying it IS, but MAY BE.

It is probably what I call 'heat soak'. When the boiler is operating near high limit and the heat call ends, there is heat collected in the hot cast iron which continues to transfer to the water inside the boiler, which is no longer circulating.

If you've ever heard an automobile electric radiator fan kick on 5-10 minutes after the car has been turned off, it's the SAME phenomenon.

You DO however have a problem with the boiler pressure.

The PSI of the system has also been high - the pressure relief valve has tripped 4 times in the last couple of weeks. Generally it has been 25-32PSI when in space heating mode and drops back to 12PSI when DHW has priority.
Read this:

http://www.doityourself.com/forum/bo...sion-tank.html

Ask questions if there's anything you don't understand in that article.
 
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Old 12-26-13, 07:29 PM
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NJ Trooper,

Thanks for your comments. The expansion tank appears to be maintaining pressure (cool at the bottom of the tank) but I have not pressure tested it. Perhaps there is too much pressure in the tank and this contributes to my issue. I will have it tested when I am able to remove pressure from the system (which I am hesitant to do because it contains a glycol mixture)...

Is is possible that air in the system is causing fluctuation in pressure and skewing the temperature readings? When the DHW recirculator pump runs I hear a lot of gurgling, but I don't know how to remove air from this part of the system to eliminate this possibility. This air never seems to be make it into the space heating circuit where the new air scoop was placed a few weeks ago.

Thanks for your help!
 
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Old 12-27-13, 04:01 AM
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I have noted my boiler can raise from 10 to 15 degrees after it shuts down due to heat soak.
 
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Old 12-27-13, 07:52 AM
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Perhaps there is too much pressure in the tank and this contributes to my issue.
Yes, too much pressure in the expansion tank can contribute to the problem... but unless someone accidentally put too much air in, how could that happen?

USUALLY and COMMONLY what happens is that the tank LOSES it's air charge slowly over time (that ALL do, it's noted in the article) and the result is that the water in the system has no place to expand to when it is heated.

Yes... the glycol presents a problem for tank service.

When was the last time the glycol was checked for PH ? This should be done periodically because the mixture becomes acidic over time.

Is is possible that air in the system is causing fluctuation in pressure and skewing the temperature readings?
Short answer, no.

Can you post some clear, well lighted pictures of your system? Maybe we'll see something that could help explain...
 
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Old 12-27-13, 08:42 AM
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Photos

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Old 12-27-13, 09:10 AM
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When was the last time the glycol was checked for PH ?
Last month during the zone relay panel installation the tech tested the PH and indicated it was good down to -24F, tho not sure of the PH level.
 
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Old 12-27-13, 09:28 AM
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Possible cause of high temp issue

I found this post which may explain my overheating issue:

Manual High limit trips on Logamatic control

I'm still under the assumption that the high PSI and high temp issues are not directly correlated though... hope that the pics can offer some possible ideas/
 

Last edited by mcckgfl; 12-27-13 at 11:59 AM.
  #9  
Old 12-27-13, 01:28 PM
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Do you know how old your boiler is?

I'm dubious of the 'dirty boiler' diagnosis...

... but after thinking about it for a little while, I came up with this possible reason why it MIGHT be the cause.

Let's say that the water side surfaces of the boiler ARE 'dirty'. This would slow the normal heat transfer while the system WAS circulating during a heat call.

If the heat transfer were slowed that much, then it stands that the cast iron would get HOTTER THAN NORMAL during burner on time.

With more heat 'trapped' in the cast iron after the pumps stop and valves close, it would stand to logical reason that the water would get that much hotter during 'heat soak'.

I used to see a 10-15 temp rise on my old boiler as Stel has also mentioned... NEVER 50 degrees!

Last month during the zone relay panel installation the tech tested the PH and indicated it was good down to -24F, tho not sure of the PH level.
I know you meant that the tech tested the FREEZE PROTECTION ...

He should have tested the PH as well.

In the second picture on the right side of the boiler there is a piece of plastic tubing coming out in a loop and ty-wrapped to a pipe... is that a CONDENSATE DRAIN line? If so, I don't think it should be running 'uphill'. Where does that tubing go?

I don't see anything else that looks 'inappropriate'... not terribly anyway...
 
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Old 12-27-13, 01:32 PM
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I'm still under the assumption that the high PSI and high temp issues are not directly correlated though...
No, I don't think so either.

Almost guaranteed that you will find the expansion tank to be low on air charge.

I would think that if you are protected to -24 that the small amount you would have to drain and replace with fresh water would not dilute the anti-freeze enough to make a big change in the protection... if any. You shouldn't have to drain more than a gallon. Remember, you are only DROPPING THE PRESSURE to zero, NOT draining the entire system.
 
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Old 12-27-13, 01:35 PM
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One more thing...

You need to keep an eye on that air vent on a regular basis. The LAST THING you want is for that to leak onto the Logamatic control!
 
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Old 12-27-13, 02:44 PM
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In the second picture on the right side of the boiler there is a piece of plastic tubing coming out in a loop and ty-wrapped to a pipe... is that a CONDENSATE DRAIN line? If so, I don't think it should be running 'uphill'. Where does that tubing go?
Yes, a condensate drain from the flue pipe to a p trap... while it appears to run "uphill" the flue pipe is actually a couple inches higher than the p trap.

I know you meant that the tech tested the FREEZE PROTECTION ...
Yes you are right. I'll ask what the PH was the next time I speak with him. I assume that was collected and verified as well.

Let's say that the water side surfaces of the boiler ARE 'dirty'. This would slow the normal heat transfer while the system WAS circulating during a heat call.
How would i go about verifying/resolving this condition? Boiler was installed March 2009
 

Last edited by mcckgfl; 12-27-13 at 03:02 PM.
  #13  
Old 12-27-13, 02:58 PM
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Almost guaranteed that you will find the expansion tank to be low on air charge.
Could the combination of glycol against the rubber diaphragm over time and cause it to loose its ability to flex with quick temperature changes on the system? It seems the PSIs can change 5-10PSI over the course of a heating cycle.... or could the air purger become blocked in some way preventing the tank from expanding at all?
 
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Old 12-27-13, 04:47 PM
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How would i go about verifying/resolving this condition? Boiler was installed March 2009
I actually don't know how to verify. I think one of the fellows in that thread you linked to added TSP to the systems and claimed that it worked... but I would be very careful about doing that... because you have to make darn sure that you get it all flushed back out again.

4 years doesn't seem like a long enough time to develop issues with 'dirty boiler'...

Could the combination of glycol against the rubber diaphragm over time and cause it to loose its ability to flex with quick temperature changes on the system?
No... highly unlikely.

Those tanks lose 1-2 PSI per year from air 'migration' through the rubber into the water. If you started with 12 PSI in that tank, and it hasn't been checked (I almost guarantee that it hasn't... it is absolutely the most neglected component in any heating system. Most techs don't even know HOW to adjust the air properly) you probably have 5 PSI or less of air pressure in the tank.

It seems the PSIs can change 5-10PSI over the course of a heating cycle
5 PSI change is reasonable. 10 PSI is pushing the envelope, but not unheard of.

or could the air purger become blocked in some way preventing the tank from expanding at all?
No.
 
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Old 12-30-13, 07:43 AM
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Circulator pump

Generally my highest PSIs occur when all zone valves/circulator pump are closed/off and boiler completes a heating cycle. If the circulator pump is off, would that prevent my expansion tank from absorbing some of the built up pressure? Not sure whether the Grundfos pump w/ check valve would close and prevent the system from neutralizing the pressure differential. Note from the photos that my setup is boiler -> circulator pump -> exp tank. Thoughts?
 
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Old 12-30-13, 04:42 PM
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If the circulator pump is off, would that prevent my expansion tank from absorbing some of the built up pressure?
No.

Don't forget that the pipes come back around on the other side of the system. It's a closed loop.
 
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Old 12-30-13, 05:03 PM
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Don't forget that the pipes come back around on the other side of the system. It's a closed loop.
But all zone valves are also closed when the pump is off... Perhaps it isn't a big issue. I see many folks have the exp tank between the pump and boiler and figured that could explain some of my issues.
 
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Old 12-30-13, 06:34 PM
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Good point about the zone valves... although they generally are not a PRESSURE TIGHT seal...

Let me look at your pics again.
 
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Old 12-30-13, 06:46 PM
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Before we go any farther, have you done the process to check and charge your expansion tank yet?

Your system has no need for the internal flow check in the pump. You have zone valves and this will prevent the 'gravity flow' problem. The installers may have (and probably should have) removed it before installing the pump.

If you have reason to believe that it's still installed, go ahead and pull the pump, and yank the flow check out and reinstall the pump.
 
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Old 12-31-13, 07:36 AM
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Before we go any farther, have you done the process to check and charge your expansion tank yet?
My tech will be here on Friday and we'll re-pressurize the tank at that time, among other things. Thanks again for your feedback and I'll let you know how things turn out.
 
  #21  
Old 01-02-14, 12:31 AM
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Possible cause of high temp issue

See: Watts Radiant: Sludge in Radiant Systems

and
Fluid Maintenance Anti-Freeze in Hydronic Systems
 
  #22  
Old 01-16-14, 08:05 AM
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I was finally able to get a technician to look at the system earlier this week and some progress has been made. We found that the PSI variations were fixed after removing the check valve in the primary circulation pump and draining a couple gallons from the system. Pressures have stabilized between 12 and 18PSI. Removing the check valve seems to have allowed the expansion tank to do its job regardless of the zone valves being open/closed.

As far as what caused the pressure to build this high - there has been a large amount of air in the recirculation loop when it runs in priority mode. The amount of air seemed to bring PSIs down to the point where the fill valve could have introduced more water into the system. That is the suspicion anyway. Once the zone valves and circulator pump kicked on, the pressures built right back up. This all seems to have been addressed now, although I still hear some air in the system after 2 days. Will be patient and see if this escapes over the next few days.

As far the high temps in the boiler - tech felt this was a result of not having a continuous loop with a mixing valve in place. There is no pump running as the heat is transferred to the water. I am suspicious that the casting could also use a flush but will wait a bit to ensure all else remains status quo.
 
  #23  
Old 01-16-14, 11:48 AM
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Why are you pumping into your air scoop/expansion? And where's the location of the feed water line?
 
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Old 01-16-14, 12:09 PM
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Why are you pumping into your air scoop/expansion? And where's the location of the feed water line?
Feed line can be seen in the second pic along the back wall - right above the drain tube that appears to be running uphill. The water feed is plumbed into the return back to the boiler. I did not design the system so I can't explain why these chose to pump into vs pumping away from the exp tank.
 
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Old 01-16-14, 02:03 PM
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mcckgfl
although I still hear some air in the system after 2 days. Will be patient and see if this escapes over the next few days.
All of the system flow must pass through the air separator.
The Indirect DHW loop never transits the air scoop.



Five Good Reasons to Pump Away! [pdf] Found here: Web-Site
 
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Old 01-16-14, 02:34 PM
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technician to look at the system earlier this week
Did the tech check and charge the expansion tank during his visit? If it hasn't been charged in 5 years, I guarantee that if it started at 12 PSI, by now it's down to around 5 or so... if you don't have pressure problems this winter, you will next winter!

I don't understand why this is not a routine maintenance item for techs. It should be.

The air in the loop to the water heater will work itself out on it's own. Give it time.
 
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Old 01-19-14, 05:17 AM
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Did the tech check and charge the expansion tank during his visit?
He did check the pressure but only to diagnose why I was getting such variation in system pressure. He did not charge the tank using the method you advise. I was expecting to flush the system and perform this recharging but this did not happen.

PSIs still seem ok after several days. Most of the air bubbles appear to be out of the system, however, I think what has happened is that they have found their way to one specific zone on the 2nd level. I get a loud thud or quick series of thuds when this zone valve closes. Does not matter if the zone is operated using the t-stat or manually, same sound.

If I close off the gate valve on this zone's return side and manually open the zone valve, there is no sound.

Assuming that this problem is caused by air in this zone, and perhaps the removal of the check valve? There are no air bleeders on this zone which makes this a bit more of an effort to diagnose. Any tips?
 
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Old 01-19-14, 07:34 AM
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He did check the pressure
And I bet that he never depressurized the system when he did so.

Unless the tank is COMPLETELY waterlogged, reading the pressure on the tank with pressure on the water side will be measuring the pressure in the SYSTEM and NOT the tank air charge. You will read the GREATER of the two pressures. If there's 5 PSI of air in the tank, when the boiler water side of the tank is pressurized it will compress the 5 PSI in the tank to the same pressure as the system. I don't get why these poor expansion tanks are so misunderstood and neglected.

I get a loud thud or quick series of thuds when this zone valve closes
Water hammer.

First check to be absolutely certain that the valve is installed in the correct direction. Zone valves will SLAM shut if installed backward.

Air in the system can aggravate a water hammer situation, but is not the root cause.

It is also sometimes caused by guess what? LACK OF PROPER AIR CHARGE in the PNET (Poor Neglected Expansion Tank).

Any tips?
In addition to PROPERLY servicing the expansion tank and making sure the valve is in the correct direction, it would be a wise move to verify that your boiler pressure gauge is accurate. Low pressure in the system will cause air to collect in the upper zones. If your gauge is lying to you (they are EVIL!) and you don't really know what the pressure is, you'll pull your hair out.

http://www.doityourself.com/forum/bo...ure-gauge.html

Sorry if I'm repeating myself, but this can't be over stressed enough. You need to KNOW that your gauge and tank are correct before going any further.
 

Last edited by NJT; 01-19-14 at 07:51 AM.
  #29  
Old 01-21-14, 01:41 PM
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I was able to resolve, at least temporarily, the water hammer situation by following advice given in this thread to remove the small spring on the honeywell zone valve. It has been quiet since.

http://www.doityourself.com/forum/bo...ne-valves.html

To recap, pressures are now ok after relieving pressure and removing the check valve. The water hammer issue started after removing the check valve, but as since been compensated for by removing the spring on the zone valve to close more slowly; i still have high temp issues when my zone valves are closed and the circulator is off - but the consensus is that this is expected behavior given my setup. maybe flushing the casting will bring the probe up to temperature more quickly, but this is debatable. for now I am playing with the REF and MAX TEMP and OFFSET settings to compensate although now having the zone panel in play has caused other issues (NO DHW priority or pumplogic awareness).

If any have experience wiring up the taco 405 to provide DHW priority with the logimatic let me know. I looked at a wiring diagram and it seems as though it is possible using the 5th zone.

Thanks again for all tips and advice, it has been extremely helpful!
 

Last edited by mcckgfl; 01-21-14 at 01:56 PM.
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Old 01-21-14, 03:13 PM
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So I guess you are saying that you checked and the valve is installed in the proper direction?

Are you going to check the expansion tank or not? No soup for you until you do.
 
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